1. Field of the Invention
This invention relates to a wafer dicing process, more particularly to a wafer dicing process employing a wafer mounting sheet that has multiple layers of different mediums with different bonding strengths.
2. Description of the Related Art
FIGS. 1 and 2 illustrate a conventional wafer-dicing process for cutting a wafer 101 into dice 106. The wafer-dicing process includes the steps of: attaching the wafer 101 to a wafer mounting sheet 100 which includes a bonding adhesive layer 102 adhered to the wafer 101 on one side and adhered to a releasable film 103 on the other side; peeling off the releasable film 103 from the bonding adhesive layer 102; attaching the bonding adhesive layer 102 of the assembly of the wafer 101 and wafer mounting sheet 100 to a resilient wafer carrier sheet 104, such as a blue tape; cutting the wafer 101 on the carrier sheet 104 with a cutter 105 to form dice 106 and a plurality of bonding adhesive layer sections 110 that are respectively adhered to the dice 106; sucking one of the dice 106 with a pick-up unit 108, such as a vacuum pad, and pushing upwardly the carrier sheet 104 with a pointed pin 107 to deform plastically the carrier sheet 104 so as to permit removal of the respective one of the bonding adhesive layer sections 110 from the carrier sheet 104; and through the use of the pick-up unit 108, moving and mounting said one of the dice 106, which has the respective one of the bonding adhesive layer sections 110 adhered thereto, to a die mounting substrate 109 in preparation for a subsequent operating step, such as a wire bonding step.
The aforesaid process is disadvantageous in that the bonding adhesive layer 102 tends to become contaminated during the aforementioned processing steps, thereby affecting adversely the bonding a strength of the bonding adhesive layer 102 upon adhering to the die mounting substrate 109. Moreover, in order to adhere the die 106 to the die mounting substrate 109 securely, the bonding strength of the bonding adhesive layer 102 is relatively strong to provide a sufficient bonding strength. However, such bonding strength tends to generate a bonding force between the bonding adhesive layer 102 and the carrier sheet 104 that is too strong to permit separation of the bonding adhesive layer 102 from the carrier sheet 104 during the sucking and picking operation, thereby causing deformation of the die 106 due to the pushing of the pointed pin 107 (see FIG. 3). There is also a possibility that a portion of the bonding adhesive layer 102 will remain on the carrier sheet 104, thereby further weakening the bonding quality between he bonding adhesive layer 102 and the die mounting substrate 109.